1. Field of the Invention
The present invention relates to a battery maintenance technique applied to an electronic apparatus in which a plurality of types of batteries can be mounted at the same time.
2. Description of the Related Art
Recently, various types of portable electronic apparatus that are driven by a battery, such as a portable information apparatus called PDAs (personal digital assistants) and a digital camera, have been developed and they are widely used.
Meanwhile, the environmental problem has become a focus of attention, and environment-friendly batteries are being actively developed. A well-known example of such a type of battery is a direct methanol fuel cell (to be abbreviated as DMFC hereinafter).
The DMFC generates electric energy by a chemical reaction occurring between methanol, which is supplied as the fuel, and oxygen, and it has a structure in which an electrolyte is sandwiched between two electrodes made of porous metal or carbon. (See, for example, “Nenryou Denchi no Subete” (All about fuel cell) by Kohnosuke Ikeda, published by Nihon Jitsugyo Shuppan, Aug. 20, 2001, pages 216 to 217.) Since the DMFC does not generate harmful waste materials, there is a strong demand for applying this cell to those electronic apparatuses listed above.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2002-49440 filed by the inventor of the present invention discloses (in paragraph [0024]) a portable information apparatus that uses a fuel cell. In the portable information apparatus, an integrated Li battery can be used as in the conventional case, as additional means to its fuel cell. When electricity is fed from the integrated Li battery, the apparatus can be operated at high-speed and high-performance mode, which use a high-level power, can be carried out. On the other hand, when electricity is fed from the fuel cell, it can be operated at an exclusive fuel cell mode in which the consumption power falls within a certain range.
In the portable information apparatus that is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-49440 filed by the inventor of the present invention, an operation mode that is selected at a time is determined depending on which of the fuel cell and integrated Li battery the electricity is fed. With this arrangement, it becomes possible to automatically set a suitable operation environment for the characteristics of the respective battery selected by the user.
In reverse, there have been no such functions developed that a most suitable battery is automatically selected from a plurality of batteries depending on the particular situation at that time, or a battery to be used is set in advance by the user for each respective situation. Accordingly, there have been no functions developed for displaying the use status of a plurality of batteries at the time, that is, from which of a fuel cell and integrated Li battery, the electricity is fed.